Trouble alarm system



June 29, 1948. A. WEAVER TROUBLE ALARM SYSTEM 6 Sheets-Sheet 1 FiledJune 10. 1942 SNQBV Il IN I( 4 .gotta om .3mm Q o. .5 a7 n M! w b3 r L IL H j D M d h .n E NQ H H E BNS o9# @WS f f Re b V 1g d me@ H [WEBS K Sie@ was d f f/. 4 El u" n IP l- T wzwwvmwlo V l nl -4 .51 E WH b Uhu wl.(3 H H Em LS HW. HW 5P RQ E Il NH Env SEM, :n .UW .D- V NE Tuvo j r 4 MUmi @nf /Nl/EN TOR A WEA VER A Tom/Ev `June 29, 1948. A. WEAVER v TROUBLEALARM SYSTEM 6 sheetssheet 2 Filed June 10, 1942 //ENTOR WEA VER A rroRA/E v www Jane 29, '1948.

Filed June 10. 1942 A. WEAVER TROUBLE ALARM SYSTEM 6 Sheets-Sheet 3IIIIHI- l /NVENTOR A. WEA VER `lune 29, 1948. A. WEAVER 2,444,078

TROUBLE ALARM SYSTEM I Filed June 1o, `1942 v e sheets-sheet 4 POLAR/ZED A r rom/Ey l June 2 9, 1948. A. WEAVER 2,444,078-

u TROUBLE ALARM SYSTEM Filed June 1o, 1942 e sheets-sheet 5 ATTORNEY'June 29, 1948. A. WEAVER` 2,444,078

TROUBLE 'ALARM SYSTEM Filed June 10, 1942 6 Sheets-Sheet 6 A r rom/AE vPatented June 29, 1948 'mounts ALARM srs'rEM Allan Weaver, PortWashington, NQY., assignor to Bell Telephone Laboratories, Incorporated,New York, N. Y., a corporation of New York Application .inne 10, 1942,Serial No. 446,521

This invention relates to communication syscentral station uponreceiving an indication off-H the existence of a trouble condition at anoutlying station to perform a roll call of all of the outlying stationsin the course of which each outlying station is afforded opportunity toidentify any trouble conditions that may exist tliereat.`

Another object of the invention is to cause the roll call operation tobe performed automatically upon the occurrence of a trouble condition atany of the outlying stations.

A further object of the invention is to provide for the transmissionfrom the central cnice of signals for selectively calling a particularone of the outlying stations which has identified a trouble condition.

A further object of the invention is to provide at the outlying stationsmeans responsive to signals for remedying an existing trouble condition.

The invention features a vibrating relay system for generating thesignals for calling the outlying stations.

The invention also features a sequence switch mechanism for controllingthe vibratory relay signal generating mechanism to eiect thetransmission of station calling signals in roll call manner. i

In accordance with the preferred embodiment of the invention twocommunication paths extend between the central or principal station,which may be an attended station, and the outlying or subordinatestations which may be unattended stations. One of these paths is atransmission path from the standpoint of the central station and at thecentral station the signal transmitting mechanism is associated withthis path Whereas at the outlying stations the signal receivingmechanisms are associated with this path. The other communication pathis a receiving path from the standpoint of the central station and thesignal receiving mechanism of the central station is associated with it,whereas the signal transmitting mechanisms of the outlying stations areassoci-ated with this path.

Both of the transmission paths are normally in marking condition andwhen a trouble condition occurs at any one of the outlying stations arelay 12 Claims. (Cl. 177--353) assigned to the detection of thatparticular trouble condition will be operated and will cause the centraloice receiving communication path to go to spacing condition, which isinterpreted by the central oice as an indication that a troublecondition has occurred at one of the outlying stations.

In response to the spacing condition imposed by one of the outlyingstations the central station transmits over the other path a signalwhich is received by all of the outlying stations to condition them torespond to their respective call signals for reporting whether or not 'atrouble condition exists at each station as called and the identity ofan existing trouble condition.

Following the conditioning of the outlying stations the central stationautomatically transmits in succession the call signal of each of theoutlying stations. As each of the outlying stations is called ittransmits a signal consisting of a single impulse in the event thatthere is no trouble condition thereat, Whereas if there is a troublecondition the station transmits a signal consisting of `a plurality ofimpulses, the number of impulses being determined by the identity of thetrouble condition.

At the central station there are a plurality of banks of indicators, onebank corresponding to each of the outlying stations and each bankcontaining at least as many indicators as there are trouble conditiondetectors at the outlying station plus an indicator for indicating atroublefree condition of a station. As ea-ch of the outlying stations iscalled by the central station, its bank of indicators becomes associatedwith a sequence device which is responsive to the signaling impulsestransmitted by the outlying stations. The sequence device advances fromnormal position one step for each impulse received from an outlyingstation and at the end of the single impulse or train of impulsescomprising the signal from an outlying station the trouble conditionindicator selected by the sequence device is operated and remainsoperated. The sequence device returns automatically to normal conditionin preparation for reception of the next outlying station signal.

It is Within the contemplation of the invention that signal responsiveselector mechanisms at the outlying stations may control devices forremedying trouble conditions such as the substitution by switchingoperations of spare circuits 'for circuits reported to be defective. Itis also 'Within the contemplation of the invention to con- `trol bymeans of the selector mechanism at the station.

contact. neotions 01k battery Yand ground to the communiciated selectorat the central oice station and also showing the receiving relaysandassociated apparatus thereat;

Fig. 2 is a diagrammaticicircuit View showing signal transmittingmechanism Aat'the fcentral' 01?-- -ce and also showing circuits fortiming the automatic operation of that oflice;

Fig. 3 is a diagrammatic'circuit view showing signal generating relaysystems at theicentralfofflee and also showingsequence devices for con--1 trolling the sequence of operations thereat;

4 is a diagrammatic'circuitview showing signal receiving andtransmitting mechanism at i Vanvoutlying station;

iFig. 5 is a diagrammatic .circuit view showing trouble conditiondetecting apparatus at the outlying station;

' Fig. 6 is adiagrammatic view indicating another voutlying station;

Fig. 7 is'a diagrammatic View showing how Figs.

1 yto 6,`in|clusive,'may be arranged tos-how a complete system, Figs. 1,2 and 3-showing the central -oflice'station and Figs.l 4,*5 and- 6showing the outlying stations; land Figs. 8 .to 14, inclusive;are'diagrammatic rep-l resentations vof various station calling signals.

General description kof system Referringvnowfto they drawingsthereference numeralA Il designatesafnormally Vclosed communioation loopwhich includes at the central offlee station the polar linerelay ILandthe alternating current Arelay i IK. The communication loop 'I Iextends through the upper armatures vand -backcontacts ofa--transnu'ttng relay 'll 'at a first outlying station shown in Figs; 4and 5 then in `serial manner through two armatures-and back conltacts oftransmitting-relays of 'other outlying stations and terminates attheupper armatures of the transmitting relay BTI of` a l'lnal outlyingAt the final outlying-station positive battery is connected to the outerupper back contact and to the inner upper front contact of re- -lay;6TI.and ground is connected totheouter upper front contact and t-o theinnerl upper'back .contact of .the relay so that when the-relay isdeenergized, which is'the normalcondition, positive battery isVconnec-tedto the upper conductor of thecommunication loop II and groundis connectedto the lower conductor of thatv loop so.

.that current will flow. over 4the loop in a given zdirection and -thisdirection of flow of current is @such as to maintain the armature ofreceiving line relay IL -(Fig. 1) on its left-hand or marking WhenrelayY BTI is: energized the concation loop II are reversed and thearmature of line relay `IL-will-he shifted to its right-hand or spacingcontact-which is connected t-o grounded battery.

At leach of the intermediate outlying stations on the communication loopII the outer upper fronti contact ofthe transmitting rel-ay. such as...the relay TI in Fig. 4, is connected to ground and the inner upper.front contactl is connected .to

positive battery, so that when relay 4TI becomes y versed,` thus causingthe relay IL-to goto its spacing condi-tion. Each of thel outlyingstations has a break key, designated 40| and BBI in Figs. 4 and -6,respectively, in one side of the loop I I and when one ofthebreak keysis operated current to the central ofce station will be cut 01T. Sincethe relay IK at the central -oice station is an alternating currentrelay it remains energized as long as current' is ilowing in eitherdirection in the communication loop and, accordingly, does not releaseits grounded armature in response to op- :eration of the transmittingrelays at any of the outlying stations. However, when current is cut olin the loop II due to the operation of one of the break keys the relayIK becomes deenergized and releases its armature. The function of relayIK will lce described later.

The reference numeral I2 designates `the communication loop upon whichsignals are transmitted from the central oice station to the outlyingstations. One conductor of the communication loop I2 is connected tothe'outer back and inner front contacts of a pulse transmittingrelay 2Pwhich is normally deenergized and is controlled by pulsing dial 28I Aandother elements, and the other conductor of the loop I2 vis connected tothe outer front and inner back contacts of the relay 2P. The twoarmaturesof relay 2P are connected to the two left-hand armatures of asending relay 2S. The outer left-hand back con-` tact and innerleft-hand front contact of relay 2S are connected to grounded batteryand the ou-ter left-hand front contact and inner left-hand back contactare connected to ground. be apparent from this that the upper conductorof the kcommunication loop l2 is normally connected to positive batterythrough the outer armatures oi relays 2S and 2P and the lower conductorof the loop is normally connected to ground through the inner armaturesof the relays. When either 'of the relays 2S and 2P is energized theseconnections are reversed, ground becoming connected to the upperconductor of the loop I2 and positive battery becoming connected to thelower conductorof'the loop. 'I'here is no circumstan-ce under which therelays 2P and 2S should be operated simultaneously as thiswouldestablish the same marking condition in the loop that exists'whenneither of those relays is energized.

At' each ofthe outlying stations a polarized receiving relay, suchas-the relay 402 in Fig. 4 and 46Min Fig. 6 has its upperwinding'connected in theupper conductor of loop I2 and its lower windingconnected in the lower conductor of the loop. At the nnal outlyingstation the loop is completed by connecting the upper winding -of relay662 to the lower winding. The right-hand or marking contact of each ofthe receiving relays, such as H32 and 53%2, which is the contact engagedby the armature when the line is in the idle (marking) condition, isconnected to grounded battery'and the left-hand or spacing contact ofeach of the receiving relays is connected to ground. Upon the 4operationof either of the relays 2P or 2S the ilow of current through the loop I2will he reversed and the armatures of all of the receiving relays willgo to their left-hand or spacing contacts.

It will i Since the automatic operation of the system results from theoccurrence of a trouble condition at one of the outlying stations, theinitiation f an alarm will rst be considered. Reierring to Fig. theoutlying station is provided with a plurality of different types oftrouble condition detectors. For example, an open door alarm relay 5D iscontrolled by a switch 502 which is open when the door with which it isassociated is closed and which closes when the door is opened, and theswitch thereupon remains closed. If desired, a plurality of switches 502associated with diierent doors may be connected in parallel forcontrolling the single open door alarm relay 5D so that the relay Willbecome energized when any one of the doors is opened. The armature ofrelay 5D is connected to ground and the front contact is connectedthrough local alarm lamp 503, conductor 504, back contact and lowerarmature of relay `5B5, conductor 506, innermost lower armature and backcontact of relay 5H, conductor 501 and winding of relay 5A5 to groundedbattery. Fig. 5 also shows a re detector device which consists of anormally energized relay 5F, the energizing circuit of which includesthe fusible conductive link 508. Upon the occurrence of a lire at theoutlying station fusible link 508 will be melted, thus interrupting thecircuit of relay 5F. The grounded armature of relay 5F is engageablewith a back contactl from which a conductive path extends through localalarm lamp 509, conductor 5I I, back contact and lower armature of relay5B|0, conductor SI2, one of the armatures and back contacts of relay 5H,in the showing of Fig. 5 the outermost upper armature and back contact,although it might be any other armature and back contact of that relay,conductor 5I3, and winding of relay 5AI 0 to grounded battery.

Trouble 'occurs at outlying station Assuming for the purpose ofillustrating the operation Iof the system that the conductive path justdescribe-d has been completed by the release of the armature of relay 5Fdue to the occurrence of a re, the relay 5AIO will be energized.` At itsoutermost' upper armature the relay 5AIO completes an energizingcir-cuit from ground through conductors 5I4, EIS and 5H, winding ofrelay 5H to grounded battery whereby the relay 5H will be energized. Atthe innermost upper armature and front contact of relay EAI!) a holdingcircuit therefor will be completed to conductor 5I2 and back through theoriginal energizing circuit, including the lower armature and backcontact of relay 5B|0, to the ground at the armature of relay 5F, sothat the relay 5AIO will remain energized after the connection ofconductor 5I3 t0 conductor 5I2 has been broken at the outermost upperarmature and back contact of relay 5H upon the energization of thatrelay. At its lower armature the relay 5AIO prepares an energizingcircuit for the relay 5B|0 from ground through the front contact andlowerrnost armature of relay 5H, conductor 5I8, back contact and lowerarmature of relay 5AI, `conductor 5I0, lower armature and back contactof relay 5A5, conductor 52I, lower armature and front contact of relaySAID, conductor 522, lower winding of relay 5B|0, conductor 523,conductor 423 -of Fig. 4 to the No. l0 Contact of contact bank 4552 ofstepping switch 4SS. At this time the stepping switch 4SS is in thenormal or idle condition with its contact brushes in the zero positionso that the energizing circuit for relay 5B|0 is merely prepared but isnot completed. At its middle upper front contact and armature relay 5AIOcompletes an energizing circuit for the transmitting relay 4TI from thegrounded front contact and armature of rel-ay '5AIO over conductor 524,conductor 424, inner right-hand armature and back contact of a Holdrelay 4H, conductors 406 and 407, middle left-hand 'armature and backcontact of relay 4C, conductor 408, inner armature and back contact ofrelay 4A, conductor 409, winding of transmitting relay 4TI, conductor 4II, back contact and armature of relay 4T2 to grounded battery. Relay 4TIthus becomes energized to place that portion of the communication loopII whi-chextends toward the central oflice station in spacing condition.The relay 5H, in addition to interrupting the original energizingcircuit for the relay 5AIO, also interrupts the conductive paths to allof the other relays in the series 5A, and at its outermost lowerarmature and front contact operates relay 551 which prepares a holdingcircuit from ground on its armature through the front contact andconductors 5513 and`458 for a Starttrelay 4ST. No further operationoccurs at the outlying station shown in Figs. 4 and 5 as an immediateand direct result of the release of the relay 5F,

Had the troublecondition at the outlying station been that of an opendoor instead of a fire the relay 5D would have become operated and wouldhave completed an energizing circuit previously described for the relay5A5. This relay would have become energized and would have caused theenergization of relay 5H fro-m the outermost upper grounded armature ofrelay 5A5, would have completed its own holding circuit to the conductor506 at its innermost upper armature, would have prepared an energizingcircuit for its 4associated relay 5B5 at its lower armature and frontcontact to the No. 5 contact of stepping switch bank 4SS2, thus cuttingoff at its lower back contact the possibility of preparing an energizingcircuit for the relay EBI@ or to any other relay in the 5B seriesnumbered above 5B5, in view of the isolation of conductor 57N from theground provided at the lower armature and front contact of relay 5H. Itis to be understood that the dotted lines in the conductor EIS and inthe conductor 52| indicate that lower armatures and back contacts ofother relays in the 5A series are included in the conductive pathextending to .the lower armature of relay 5AIO. It will also beunderstood that there may be more than vten relays in the 5A and 5Bseries for responding to the detection of additional trouble conditionsand in the event that additional 5A and 5B relays are required, thelower back contact of the relay 5AI 0 would have a connection to thelower armature of the next relay in the 5A series. All of the relays inthe 5A series have their middle upper armatures connect-ed to theconductor 524 so that upon the operation of any of those relays theenergizing :circuit for the relay 4TI is completed.

Central office responds to trouble occurrence The imposition of aspacing condition on communication loo-p II by the relay 4T! causes theline relay IL at the central loflice station to go to its right-hand orspacing contact, the relay IK remaining energized by the reversedcurrent in the loop II. The armature of line relay IL completes anenergizing circuit for slow-operating relay 2R from. grounded battery atthe spacing contact of relay IL through the armature, conductor I0 I,right-hand armature and back contact of relay IQ; conductor |02;Aconductor 202,-, and -winding .of `relay`2R, to ground. A circuit isyalso completed -rom conductor |02 through conductor -IIlG and windingof relay I iJI to ground, so that'relay' I 01 becomes energized. rIlhearmature and'back contact of relay-l 21' arein the venergizing circuitlof re- 'lay IIQ, but as this relay had'not` yet been ener-.gized-,fthe' operation of relay I'I has no immediate reflect. Relay7IIIVI serves to time the operation of relay-IQ,r as will be describedlater.

' The `armaturefof "relay 2R is connected to groundedbatteryanduponengaging -its front contact completesacircuit for the flowofcurrent through. resistorf2-03. The battery connection tothe armature ofrelay 2R is positive and Ac ondensers 236 and 2631 connected in seriesacross resistor 2il3become charged to |change the potential on thegridfof'y an electron discharge tube 2B from negative with respect tothe cathode, as normally provided by the negative terminal of a biasingbattery 2938, to'apositive potentialwith -jrespect' to thecathode,whereby the tube 2B is rendered conductive. rThe delay aiordedby the slow-operating characteristic of relay 2R provides lfor operationof tube 2l?,l only in response to along .spacing-'condition' of loop II-so .that the` tube 2B shall notibe :operated'in response to hits onthe tential on Vthe grid of tube 2B to a negative value relativeto thecathode. Thus the `combination of lresistors rand condense-rs firstoperate and then afterl an interval cut ofi the tube 2B and theinl'terval during which the tube isl operated is independent of relay2R, which remainsoperated.

The plate circuit rof tube 2B includes the relay 2U'-which is:energized'during the interval that tube 2B: is' conductive.

energizing circuit extends from the grounded Airont contact of relay 2Uthrough the'anrnature,

'conductor 2l I, conductor 2I2, conductor SI2 and winding of steppingymagnet -3C to grounded 'battery. "Stepping switch 3C is preferably ofthe type iinwhich the contact brushes are `advanced upon :the backstroke of the stepping magnet and accordingly the contact arms arestepped to .the No.` 1 contact of each bank when the tube 2B is cut off.

With the brushes of stepping switch' 3C advanced to the first position,no circuits are established through contact banks 3CI and SC2 becausetheir No. 1 contacts have no connection.

Ground is connected over the brush andNo. 1 contact `of bank 363 andover conductor rSQI to the contact No. 12 of contact bank l3BElisoil-ncrmal L a v'ground connection ris. extended The grounded frontcon- Atact completes an energizing circuit forfthe step- Vping'rnagnet3C of a stepping switch which will lbe referred to generally by thereference number *3C and which' has six c'ontactbrushes and banks Jofcontacts identified 3CI to BCS, inclusive.- The 8 over conductor 3 I 9,conductor 24 I Sly-and conductor H9 to the left-hand yfront contact ofrelay IQ, the cooperating armature of kwhich is connected toone.terminal cf'the'left-hand winding of the relay, the other terminal beingconnected to grounded battery. yThe left-hand winding of the relay vIQis a holding winding but since, as pre- 'viously stated, the relay IQ isnotyetY energized, a

holding circuit for that relay is merely prepared at this time by theycontact bank -3C`5. The No. 1 contact ci the bank 366 is connected byconductor 32|v to contacts Nos. 15 and 16 of contact bank =3B5 of thesequence switch 3B which has notyet advanced from its `normal positionso that no electrical circuit is established.

From the foregoing it will be apparent that the only operation performedby the Stepping switch 3C in the rst step while stepping switch 3Bremains unoperated is the energization of re- ,lay 2W. At its right-handarmature and front contact the relay 2W connects grounded battery `overconductor 222, outer right-hand armature and back contact of a relay 2X,which at this time is deenergized, and Iconductor 223 to the arma- Itureof a relay ZY which at this time is deenergized and as the relayfZY hasno back contact connection, no electrical circuit is completed. At itsleft-hand armature the relay 2W completes acircui-t from the groundedouter left-hand armature and back contact of relay 2X, conduc- Centralofce sends preliminary signal At its left-hand armatures the relay 2Sreverses the battery and ground connections to transmitting loop I2,thus impressing a spacing condition on the'loop I2.` The innerright-'hand armature of relay 2S is operable between back and frontcontacts,'both Vof which are connected to ground. The armature isconnected to the grid side of the input circuit of an electron dischargetube 2C and the input circuit includes a resistor and battery in seriesbetween the gridy and cathode, with the battery poled positively towardthe grid', a condenser between vthe grid and cathode, a second resistorand battery' in series between the grid and cathode, withthe batterypoled negatively toward the grid for biasing the discharge tube tocut-off, and a varistor between the iirstmentioned resistor and the gridside of the condenser. When the right-hand inner armature of relay2S isin engagement with either of its contacts the condenser is charged tonegative on the gridside by the negative biasing battery and the tube-is biased to cut-off. During the interval in which the inner right-handarmature of relay ,ZS is in transit from one contact to the other groundis removed from the gri-d side of the'input'circuit and the batterywhich is poled positivetube 2C continuesto be conductive is prolongeddue to the fact that the varistor prevents the condenser fromdischarging directly back to ground when the armature of relay 2Scompletes its transit and the return of the grid to -its originalcondition of negative charge on the grid side is delayed by the gridleak resistance of high value. The plate circuit of the discharge tube2C includes the relay ZY so that that relay is energized during theinterval that the tube remains conductive. i i

A battery connection from the right-hand armature of the relay 2W to thearmature of the relay ZY has previously been traced. With the relay ZYnow energized this battery connection is extended over conductor 236,right-hand armature and back contact of relay 2V, conductors 231 and331, and winding of stepping magnet 3B of the Stepp-ing switch,hereinbefore also referred to as 3B, to ground. Upon the cutting off ofplate current in the discharge tube 2C the relay '2Y is released and thestepping magnet 3B advances its associated brushes to their rst positionon its back stroke.

The outer right-hand front contact of relay 2S is connected to batteryand its armature is connected by conductor 238 to one terminal oi thewinding of relay 2Z the other terminal of` which is connected byconductors 239 and 339 to the outermost left-hand back contact of relay3AA, the` armature of which is grounded. Thus the energizing circuit ofrelay 2Z is completed and that relay operates to interrupt theenergizing circuit for relay 2S. The relay 2S releases slowly and (l)restores the loop I2 to marking condition; (2) momentarily removesground from the grid side of the input circuit to discharge tube 2C toactivate the tube and thus` effect the advancement of stepping switch 3Banother step; and `(3) interrupts the energizing circuit forthe relay2Z. 'Ihe relay 'ZZ has a` slow-to-release characteristic, and upon itsrelease it again completes the energizing circuit for the relay 2S,again sending the loop I2 to spacing, advancing the brushes of steppingswitch 3B another step and interrupting its own energizing circuit. Fromthis it will be apparent that the relays 2S and 2Z form a vibratorysystem for sending out upon the communication loop I2 alternate markingand spacing impulses and for advancing the brushes of stepping switch 3Bone step for each transition of the line condition from marking tospacing or spacing to marking. l

The odd-numbered contacts of bank 3B2 down to and including contact No.9 are connected to even-numbered ones of the contacts of bank 3CI andsince the brush associated with bank 3CI is now in engagement with thecontact No. 1 no conductive path is completed to the ground on thatbrush as the brush of contact bank 3B2 is advanced step by step. Thebrush associated with contact bank 3B2 is connected by conductor 333 tothe right-hand armature and left-hand front contact oi relay 3AB. Theright-hand back contact of relay 3AB is connected through the winding ofrelay 3AA to grounded battery, so that the relay 3AA will becomeenergized when the brush of bank 3B2 picks up a ground connection. Theodd-numbered ones of the contacts of bank 3B2 are also connected by agroup of conductors through the windings of odd-numbered ones of therelays represented by IDI and IDIIJ but as those relays have groundedbattery connection of the same polarity as that connected to the relay3AA neither the relay 3AA nor any one of the 10 4relays IDI to IDIU willbe energized as the brush associated with contact bank 3B2 advances overthe odd-numbered contacts down to and including the No. 9 contact.

The even-numbered contacts of bank 3B4 are connected to odd-numberedcontacts of the bank BCI, excluding contact No. 1 of bank 3CI, and toeven-numbered ones of the series of relays IDI to IDI. The brushassociated with contact bank 3B4 is connected by conductor 334 to theright-hand front contact and left-hand back contact of relay 3AD and theleft-hand armature of relay 3AD is connected through the winding ofrelay SAC to grounded battery which is of the same polarity as thebatteries connected to the windings of the relays IDI to IDID, so thatthe relay 3AC cannot become energized during the advancement of steppingswitch 3B while the brush associated with bank 3CI engages its No. 1contact.

All of the contacts of bank 3B3 except the zero contact are connectedtogether and to ground and the brush associated with the bank 3B3 isconnected to conductor 3I'I to provide a substitute ground for theenergizing circuit of relay 2W which ground is not independentlyelective at this time since the brush associated with contact bank 3C4has maintained relay 2W energized through the No. 1 contact of that bankas stepping switch 3B advances.

The earliest connection in the bank 3B5 is at contact No. 15 and in thebank 3BG is at contact No. 12 but when the several brushes of steppingswitch 3B reach their contact No. 11 the brush associated with bank 3B2finds ground on its contact No. 11 and completes the energizing circuitfor the relay 3AA. VThe relay becomes operated and at its outermostarmature it interrupts the energizing circuit for the relay 2Z. Byreference to Fig. 8, which represents the signal that is beingtransmitted by relay 2S, it may be seen that the energization of relay2S puts the loop I2 in spacing condition and causes the oddnumberedsteps of stepping switch 3B and that the energization of the relay 22causes the loop to return to marking condition and effects theeven-numbered steps of switch 3B, this being accomplished by cutting offrelay 2S. It will also be seen that incident to the eleventh step of thesequence switch relay 2S is energized and seeks to energize relay 2Z.However, relay 3AA prevents the energization of relay 2Z and thereforethe energizing circuit of relay 2S is not interrupted and the loop I2remains in spacing condition for a longer interval than the previousspacing intervals, under the control of other factors which Will now bedescribed.

The middle armature of relay 3AA cooperates with a front contact that isconnected to grounded battery and the armature is connected byconductors 34|, 342 and 242 to conductor 23| extending to the Winding ofrelay 2S so that relay 2S will be held energized should the relativetiming of operation of relays 2S, 2Z, 3AA and stepping magnet 3B be suchthat relay 2Z operates and interrupts the energizing circuit for relay2S before the energizing circuit of relay 2Z is interrupted at theleft-hand armature and back contact of relay 3AA. This is desirablesince the slow-release characteristics of relay 2Z might permit relay 2Sto release and return the loop I2 to marking condition. The innermostarmature and front contact of relay 3AA completes the energizing circuitfor relay 3AB which operates. At its left-hand armature and frontconartefacts:

11 tact relay' can `vestablishes its @Warhol-ding. circuit; fromgroundson contactNoirJ-ll officontactibank 3132` `through vconductor13362::- At its fright-.handr armature and back contact thecrelay .SABinter: ruptsy the energizingcircuit for the .relay SAA which releases..Relay 'SAAhas a slow-release characteristic'andupon; releasingv itremoves .the holding battery connectionior the relay 2S and completesthe energizingcircuit for the relay 2Z which becomes-energized torelease the relay 2S. The-spacing lconfdtio'nxon'loop I2 endures untilrelay 2S has :releasedat which time .the loopagaingoes to markingcondition and discharge tube 2C is-operated'to advance stepping switch3Bfto its twelfth position.

Thereis no `connection tocontact No. 12 of bank SBZ andino' changeofcondition is encoun. teredby anyfoflthe'other. brushes ofzswitch 3B'.

except'in bankeSBfwhere afconductor extends from contact No. 12 tocontact No. 1 of bank SC3.. HereY groundiis applied from the-brushassociated with 'bank 3C3.over conductor Bill;v contactNo. 12 andbrush of ibank Bgconductors. int-Band` E43-and the wind-ingrof relay 2Xtoxgrounded bat.- tery,and'relay=.f2X ispoperated.

Atlits` inner left-hand armature vand frontcontact therelay 2X 'providesa holding circuit' from conductor 2H, Which is-receiving ground fromcontact-ibankiltfat. everystep of'vthe stepping switch and is holdingrelay 2W.; At its outer lefthand"'arniature fandY-back contact `the`relay 2X interrupts-I the previously straced energizing circuitlforfthe relay 2S,1so'.as .to terminate the vi.- bratory operati'on'frof:relays 2Sv and 2Z, with relay 2S-remaining`.in released condition, inWhichAtl was ,placed by.` the operationof relay .2Z. followingthefreleaseof relay SAA', andzthusfmaintaining steady marking conditionof communication loopA 12.?, At its buter lrightehand. armature `therelay transfers; thefenergizing.` circuit for stepping'` magnet 3B fromYal direct"connection4 through the conductor'f33i! .tow'an indirectconnection `through the -interrupterncontacts of stepping#magnet 3B,ythev circuit being: traced from batteryfthrough theright-hand'frontfcontact and .armature of Vrelay 2W; conductor.2225.outerright-hand.v armature, andfront'contactfofarelay 2X,Vconductors 244 and SMLfinfterrupter :contacts -of-stepping.- magnet 3Bthrough"thefzwin'dingof the magnet to. ground. l The fstepping;magnet 3Bthus operates in buzzermanner;` an'derapidlyf and automaticallyIadvances its' brushes aroundatotithe zero yor rest position.rv Until':ani fadditionalcontrol effected by'fthe. .relay4 2X`-isydescribed.ritt-willi. be. assumed merely that l thefstepiline.k YSwitch`3Bfjstarts tooperate in buzzer man-ner and `thefbrnshes.lea'vecontactsNo. ,12. 1

At its inner right-hand armature andy front' contact the relay 2Xcompletes theenergizing cir* cuit-forLv the relayx.2V from ground.through thearmature andrrcantS contact; conductorfzd yfand, Windingfof`relay 2V iso-grounded battery. The re*- lay ziffurther;V interrupts atits rightshandarrna-v ture and backfcontact the directvenergizing-1cir"- cuit-forL the`I stepping lmagnet 3B ,for Which thebuzzer-energizing circuit has already been rsubsti-l tute'd". At itsinnerleft-hand armature and backf contact the relayfZV) furtherlinterrupts the energizing circuit, forthe relay 2S which .has-already'been interruptedzby .the relay 2Xv Theoperation.- offrelay 2V causes itsouterleft-hand armature to belvdisengaged :from a back contact fromwhicha conductivepathgnot yet identied extends-to the No. -2 -contact.=of the stepping, switch .bank113C2..r. Since the-brushes ofy thestepping.: switch 3C are 1 not-yet 1- in engagement' with their: No 2contacts;

theilrelay 2Vtdoesanot'tinterruptanelectrical cir-a cuit and romjthi'szitlwill be apparentthatthe ope; eration `of relayl 2V atx-thistime. performs'nodirect operation; i.. i i

l When' the fbrush associated with'y .thezzcontactf bank .3BEv'encountersfthe contact:No.oltotzthati; bank a; .circuit iscompleted;throughlthel contacts. Nos; 15V i and :5.16, i which areiconnectedatogether;T fromrgroundlon l. the'` brushfiassociatedI .withbankvl wf 306 through thezNo't-il.. contactmf `thatzbank, con-.x

w Asupreviously set forth the'A outer .armature `.ofi relay 2U connects.ground ,to .theaconductive 'path'L consisting of yconductors 2 k2. and@l 2rextendingftof stepping `magnet 362s@ thatfthe magnet lisienerfIgized preparatoryA toistepping the: brushes to the.;- No. 2. contacts;-Asthefbrushes oistepping` switch; 3B'=passfr'o1n:contact'No 16 .tocontact .Nor 1'7,"v relay I2U Yis vreleasedvand.then-brushesofvstepping`switch .C'arie steppedto the Neo2-contacts. lThef brushes of thestepping switchz3Bi'in-the mean'- J time;continue'stoy be advanced.to-their zero positions'.` andino .circuitichanges I are: eiectedasnthe= brushes complete ztheirrfcycle and'move intornor-Y mal orzeropositionexcept Vthat asthe :brush associated with contactybank:3B3.g moves out offen gagementwith thellast ofxtheinterconnected/icona..-

' tacts andinto'thefzerofposition,grourrdon the in'-Y terconnectedcontacts is removed fromconductors 3H andi I' in .thefholding irouitsfortherelays. 2W :and 2X so. that. those relays. are released .andrv 5..the-xfrelayi2vfiwhich Was held.. energized .-'by the relayZX'is alsoreleased. Y l

. Befrev describinguthe-isequenceoffl operations whichf. occurs .f as:.aaresult of Vthe-stepping Lof the: brushes 'of stepping.- switch' Y3Cto theflNo; 2J con# m tactaftne* eiect produced :at .ther-outlying;stations. by f the,` transmission ofy thefalternate :marking and r.spacingI signals, inl: accordance withithefpatternl shown vin Figu duetorth'e vibratory operationfof. the lrelays: ZSEandJZZias influencedfollowingi the 4K5l eleventh-5transitionbyfthe relays SAA# and 53AB'-Wilt be described. l Olfiz'tlvying stations respond-l. to preliminary lsignal in AFigi 4,' the' 'armature' o iijl thexpolarreceiving.

relay 402 'is connected;byjcorrductorAI6 to one; terminal ofVa'condenser i 1 ",f;tl;le .other terminal of which is connecter'tojoneterminal of a polar magnet 41 Bi'the otheriterm'inal of which is con-.

nectedftofground. The pola'rIrriagnet418I is thei operatinginstrumentality l ofiL af stepJby-step selector fmechanism`A -suclrf-asjv .that l disclosed yin Patent; 1,`34=-325 6,Lgran-ted*Nine-15311920;L to AJ, C.

Field;` The disclsure'ofthe" patent isgin'corporated-herein'byireferenceasfpartofthe present T' pulses of'cur-rent The armature is providedwithj Y from ytheneutra/1f' position@ to fone side'gqtiieii to:

the vop'p'osite-`-side-and-Jbackft the neutral fposition; 4The contactWheel. ora di-'scis provided witl'rselectivelyYlocatdipinsawhich:willfbe engaged by a cheek pawlV` sooiatediwitlithearmature' lei/erf,

when@thaanatcrealever is` momentari'ly-l per;`

" 13 mittd to be at rest in the neutra'l position after having beenoperated through `a plurality of cycles or half cycles and such pawlprevents the contact ldisc or Wheel from returning to normal positionunder the iniiuence of its restoring spring. When a plurality oi suchselectors with differently located stop pins respond to signalsconsisting of current reversals, a, pause in the transmission of'signalswill cause those Which have stop pins, presented to their check pawls tobe held in the positions to which they have been advanced, Whereas allselectors which have no stop pins in those positions Will return tonormal position under the influence of the disc restoring springs. Whentransmission of current reversals is resumed, those discs Which wereheld in advanced positions are further advanced from those positionsWhereas in all oi the selectors the discs of which were restored tonormal, those discs are again advanced from the normal position.

Step-by-step selectors of the type disclosed in the patent to Field areprovided with' contacts which are engaged by a contact arm carried bythe step-by-step wheel or disc for the completion of electricalcircuits. completed `through the check pawl as a circuit element, sothat as th'e Contact arm comes into engagement With a contact, as it isbeing advanced step by step, an electrical circuit is not completed ifthe advance continues but only if there is a pause in the signal trainwhich permits the check pawl to engage a stop pin and hold the disc orwheel in the position to which ithas been advanced. When selectors ofthis type are employed in a system, all may have their electricalcontacts in the same relative positions, such as in the eleventh,thirteenth, fifteenth and seventeenth steps as shown in Fig, 4. Takingthe thirteenth step as an example,.it is not necessary to send thirteenimpulses in regular succession in order to cause the Selector to reachthat position. The selector may be provided with one or two stop pinsintermediate the rest position and the thirteenth step, whereby thethirteenth step may be reached by the transmission of sets of impulseswhich total thirteen, with a pause between each two sets of impulses.During the pause at the end of the iirst set of impulses those selectorswhich have stop pins in the positions to which' the discs of all of theselectors have been advanced, will be held and the discs of theremaining selectors will be restored to normal, In a two-digit systemonly one disc would be so held and all of the others would be returned.In a three-digit system a plurality of discs would be held and theremainder would be restored to normal. Upon the resumption oftransmission of impulses, all of th'e selector discs would again beadvanced, some from their initial positions and one or more from itsadvanced position. At the end of the second group of impulses the discof one selector closes an electrical circuit if the system operates on atwo-digit call and all of the remaining discs return to their normalpositions, with the exception that the second set of impulses maycorrespond to the rst digit for some other selector in the system andthe disc of that selector may be held in its iirst digit position,although it will close no electrical circuit in this position. Followingthe closure of the electrical circuit the transmission of a singleimpulse will restore all of the selectors to normal. If the system isoperable upon a three-digit call a plurality ci discs will be held atthe end of the second set of impulses, the number being smaller than thenumberfwhich The electrical circuits are 14 were held at the end of the'rst set of implses. At the end of the third set of impulses only one ofthe discs will have been advanced to a position to close an electricalcircuit.

In the arrangement shown in Fig. 4 only a single battery on the markingcontact of line relay 402 is employed for energizing selector magnet 4I8but the condenser 4II serves to give a polar effect to impulses. In theidle condition th'e condenser is charged positively on the side towardthe battery and negatively on the side toward the magnet 4I8, and nocurrent is flowing through the magnet. When the relay 402 goes tospacing the condenser discharges through the magnet 4 I 8 and rocks thearmature to one side of the magnet. If the relay 402 returns to markingbefore the discharging current has died out condenser 4II will berecharged and the charging current will rock the armature to the otherside of magnet 4I8 without any pause of the armature in the neutralposition. A pause in the signaling train of either marking or spacingnature will permit the armature of magnet 4I8 to go to its neutralposition because the charging or Idischarging current for condenser 4I'Idies out before the end of the pause. l

Since as shown in Fig. 8 the signal transmitted by the relays 2S and 2Zconsists of eleven transitions followed by a `pause of spacing nature,the contact discs of all of the selectors in the system will be advancedto the eleventh step. At each of the outlying stations a similarelectrical circuit will be completed which, in the case of the stationshown in Figs. 4 and 5, extends from grounded battery through theselector disc and contact arm, the eleventh step contact, conductor 4 I9, and winding of relay 4SI to ground. At its left-hand armature andfront contact the relay 4SI prepares a holding circuit for the relays4S2, 4S3 and 4S4, none of which is at this time energized. At its innerright-hand armature and grounded back contact the relay 4SI removesground connection from a relay 4B, Which has no eiect because the relay4B is not at this time energized. At its outer right-h'and armature andgrounded front contact relay 4SI completes the `energizing circuit forthe hold relay 4H through conductor 426, conductor 42'I and theright-hand Winding of relay 4H to grounded battery. The relay 4Sl alsocompletes the energizing circuit for relay 4E over conductors 426 and428 and winding of relay 4E to grounded battery.

At its left-hand armature and front lcontact the relay 4E establishes aholding circuit for relay 4H over conductor 429, inner left-handarmature and front contact and left-hand winding of relay 4H to groundedbattery. At its inner right-hand armature and front contact the relay 4Eprepares its own holding circuit from ground through its right-handwinding, conductor 432 and conductor 4I6 to the armature of line relay402. At its outer right-hand armature an-d front contact relay 4Eprepares a holding circuit for the relay SBI, which will be tracedlater, Relay 402 returns to marking following the long spacing pauseafter the eleventh step and completes the holding circuit for relay 4E.The relay 402 also steps the discs of all of th'e selectors to thetwelfth step, where none of the selectors has a holding pin andaccordingly all are returned to the normal position, thus releasing therelay 4SI vand corresponding relays at all of the outlying stations andleaving the relays 4E and 4H energized and held fat all outlyingstations.

lef'erence; is `made tolj the {factl that, the `relay f AI101fhas been,assumed tobe' energizeddu-e.-to?v theoperation of. the fire detectionapparatus at the station shown in Figs. .4 fandff andlthat this.

hastcausedltherelay `llTI to bei operated to..-plac'e thercommunicationloop'l I .leading to vthe cenA trai 4oice station inspacing, condition.. Thevfol,n lowing sequence of yoperations is.4predicatedfupon this;l assumption `but the operational: differenceswhichrwould result froma trouble-free condition.

of, the station shown -in Figs. 4 and 5 Willalso be mentioned;

.At its outer ighthand. 'armature ,and ffront, contactpthe relay` 4H.connectsground through f,

conductor l 4:armature .fand back contact l of.A relay vllGr,`conductorsrllt` Iand 534, back contact ,and

lower armature of relayBI ,tothe second lowest arrnaturevof,` relay1Ill-L. ,From thefback,contact withwhich thisarmature ofurelay"5H'cooperates, conductor .531 extends tdoneterminalfof thel relay; 5AIvvthe other; terminal @of vwhich is -connested-to.groundedgbattery.Thus-ii relay 5H were not-energized,l the relayf5AI would becomeenergizedrto indicatethat no trouble condition existed atthe stationand-,the relay 5AI Wouldbe front Contact to conductor 53E vand .to theouter rightehandarmatule yand ifront contactfof rel-ay.

4H1 .through conductor 538.'- The relay AI ywould inqturnenergze .relay5l-Iso` that after relay 4H hasbeen operated, relay BIrlwillloel in theoperatedcondition. Since it hasbeen assumed that relay 5H. Waspreviouslyenergized ithe: relay 5AI Y does not-become energized.

At its outer left-handarmature and frontcon-k tact the relaylllllconnectsground over conductorl 44 It Winding .oigrelay lIT2,.onductor'tllzg inner?- most lowerarmaturegand frontco-ntact `of relaylIITI to grounded battery.- Thesingle*armatureof the relayl-llzremovesbattery from the cony ductorAII .in the energizingQrcuitforthe relay TIfsothatthat relay is deenergized. The relay KITE.: is. sloWTto-releaseandy -accor(.lingly an. interval elapsesfrbeforegit releases to restorethe ComunicationA loop II toward 'thefcentral. olce station to markingcondition. Atits inner-,righthand armaturetherelay IH transferstheAground connection suppliedover conductoiui beginning i atltlre uppermiddle` armature and Afront contact` tact =andouter armature of `relayIIA; conductor` llbacl; contact anniI outer lethandarmature of relay IICand conductor Illltogthe middle armaturefof start` relay AST. y The back)contact- With Whichthe armature of relaySI'` cof operates isconnectedto groundedbattery but as the relayis not energizedatthis'timeandrrelaym ATI is. in process-z of being. .released an,electrical'. circuity :through the stepping `magnet #ISS is. not:

yet completed.'

Whenl relayA STI releases;fitnopensgthe;enerf gizingcircuit forrelayIII'Z which isjalso aslowrelease relayy and which upon release-restoresthe. battery connection to conductor llgtamextendingf to Athe winding`offrelay IITI.; However,v theflatter relay WiIln'Otat this time bere.energizedbecause` ground connectionf. has,` Irwell:-y 1'em0ved;;ttheinner right-hand armaturebfzrelay AH:

325 held from its innermost upper armai'rureandy 161" prepares to:conducir: roll-f f'ctlfr of."

outlying stations.:

The operations ywhich take place' at the outfA lying stations/inresponse to reception Yofthejsig-'j nalY represented'in Fig. 8occurduringljthe'- long spacing interval following theeleventh'transition; Following `this there is a steady markinginterval"v on loop I2the duration of Which isjdetermned, by the timeinvolved in the restoration of 'stepg ping switch 3B to normal and bythereleasetime of lthe relay L2V Whichyi's slowjto release, Therestoration 'of the marking condition on .the com;` munication loopIIdue tothe 'release' of'relayj IITI causes the relay ILto be driven tothemark# ing condition whereby .the'relay 2Rfisv released. Thisdoes notcause tube 2B toj operate;since` positive battery' .is disconnected*from'. condenser 206." The relay IL also releaseth'e relayA |01', lthe'purpose of which Willbe described later. r

`With y.the brushes vof stepping svvitch'3C"adA vanced to the No.2'contacts as previously :lescribed, a circuit is completed from groundon" the brush vassciatetiv with `bank aol through the, No.2 Contact ofthe bank, conductor 35I'A,"con ductor 352A, conductorlIBZA inFig.1andWind-" ing of relay IDIfto grounded battery. Relay IDI" thusbecomes energized and attracts itsarrnatures, of Which there .are asmany asthere may Y beg-troublel conditions at outlying stations to bevregistered;y The armatures oflth'e relay'IDIare connected to individualcontacts of lbank IAI of avstepping 'switch IAL The `frontcontactslof-the relay IDI areindiyidually connected to the Wind?ingsnofzrelays, such as relays IEI, IEIfand'IEZll', which control'individual alarm A'lamps IB I; IB I i and IBZEiJ'-Additional"conductors v35 IB to 35v-IJ are connected 'to contacts No. 3to Noi 11,'"inclusive, ofbank-@CI and extend through coz'iductors"352BIto 3525' andv conductors I 52B to |525 to additionallrelays ofthe IDseries, of which only thefrelaLy-f I Dl'fis shown. lAll of the ID relayshave'ftl'i'eir"v` armaturesv connected to" theconductorsextending to thecontacts oisteppin'g switch-l bank; IAI and their front v,contactsconnected to individual re# lays-fior controlling 'alarm' lamps.Th'usthe front# contacts oftherela'y IDM) are connectedtoflampfcontrolling relays,l of `which y the relays IFIQv IFI II an'dlFZ'areshoWn. It'v Will: be understoodthat there will be as many oftheIDseries-r'elays'asil therev are Aoutlying stations in the'system andthatrtherefwillifbef,as many relays in eachfof the series: representedby -'the I E''relays" and fthe.. IF relays in lFig. l 'as 'there are itrouble .conditions to.;be. registered...

:'Uponzthearelease'of 'relay I'I "a ciro'uitisv com-.1f pleted .fromthe.. grounded-.brush associated with': Contact .bank 364 through theNo.;..2 "'c'ontaot of? that bank, `conductors. 3If4,12!4 :andIIA`4,right.-f hand :Winding oi. relay` IQ, Yconductorel I:3`,:;armafture and baci; Contact .of relay. |01; assumingthat';

relay .Itl' has released, to` grounded;battery-.fv At.- itsLlef-t-handarmature and frontficontact the re'.u layd Q. completes a holding.circuit vfrom i ground-y edlbattery through-:the: lefteliandwinding ofthe relaygconductors -I I9,` 2I.9;'and.3I'9--,th1'ough thevinterconnected conta-.cts of ycontact .banks- 3GB, all oflwhich :areconnected.y together except; the Zero Contact;Y to the; grounded brushMthroug-h i contactH No.; 2 io.- that: bank which the brush.l at: thistime:- engagesr It 1 will 'beapparent that; relay; IQ rwlllijbe:;held-energized until therl brushes offstepping switch 302 havecompleted a.-cyclefandfh-ayebeen' restored fto their zero positions: At:its rightfhanda armaturetheV relayY lQrtransfers- -ther;-conneotionrofrxthearmature 4ofi: reoeivinggline rela-WI Lffrom the energizingcircuit of the relays |61 and 2R to the stepping magnet of steppingswitch IA through the right-hand front contact of relay IQ, lconductorII6 and conductor II1, `winding of stepping magnet IA to ground. Aconductive path extends in parallel with the one just `described, fromconductor II6, throughv conductor II-8 and winding of slow-release relayIM to ground.

Neither .the stepping magnet IA nor the relay IM will become energizedat the instant that relay IQ is operated, because relay IQ can becomeenergized only when relay ILis in marking condition with its armatureengaging the dead left-hand or marking contact. The reason for this isthat the energizing circuit for the relay IQ is controlled not only bythe arrival of the brushes of stepping switch 30 at their No.2 contacts,but also by the relay |01, and the relay I61 is controlled by the relayIL prior to the energization of relay IQ so that the relay I 01 cannotprepare nor complete .the energizing circuit for the relay IQ until therelay IL has been restored to marking condition. The purpose of thistiming control of the energization of relay IQ by the receiving relay ILis to prevent the energization of relay IQ before the loop II has beenrestored to marking condition due to release of the relay 4TI at theoutlying station wherea trouble condition exists, under the control .ofthe Hold relay 4H at that station. If this timing control were notprovided and the stepping switch should be stepped to the No. 2 contactsbefore the relay IL had gone to marking condition an energizing circuitfor =the stepping magnet IA and the relay IM would be compieted by therelay IQ and the energization of these instrumentalities is not desiredat this time. Since the right-hand armature of relay IQ effects atransfer of the connection from the armature of relay IL, the energizingcircuit for the relays |61 and 2R are opened at that point so that thoserelays will not respond to nor follow any signals thereafter receivedfrom outlying stations during the time that relay IQ is held energizedfrom contact bank 305. v

The release of the relay 2Vat the end of the rst cycle of steppingswitch 3B results in the completion of a circuit from grounded batteryon the brush associated with the stepping switch bank 302 through theNo. '2 contact of that bank, conductor 356, conductor 256, outer backcontact and outer left-hand armature of relay 2V, conductor 251,left-hand armature and back contact of a relay 255, conductor 266 andprimary Winding 258 of a transformer to ground. A circuit is alsocompleted in parallel with Ithe primary 258 of the transformer fromconductor 251 through conductor 254, left-hand winding of relay 255 toground. Relay 255 h-as a slow-to-operate characteristic and a-ccordinglyits operation is delayed. The rise in flow of current throughtransformer primary 258 will produce an impulse in the secondary 259 ofthe transformer which is connected acros-s the input circuit of anelectron discharge tube 2A between the grid and cathode of that tube.The polarity of the impulse will be such as to charge condenser 26Ipositively on the grid side of the input circuit, thereby overcoming theeffect of the negative biasing battery which is in series with the highvalue grid leak resistor connected between the grid and cathode. Tube 2Awill be rendered conductive and will continue to conduct until thecharge on condenser 26| which was produced by the impulse in thetransformer leaks off through the grid leak resistor and nega- 259 apulse in the opposite direction which charges condenser 26| in thereverse direction. Thus the tube 2A is cutoff if current had not alreadyceased to flow inits plate circuit.` It will be apparent from this thatrelay 255should be sufficiently slow to operate, Ithat it will not openthe circuit of transformer primary 258 until tube 2A has operated relay2 6 `.which in turn has operated relay ZBD. The relay 255 establishes aholding circuit for itself from grounded batly through .the right-handwinding of the relay, front contact and inner right-hand armature,conductors 265, '365 and 314 to the No. 2 contact of contact bank 306which at this time is engaged by its grounded armature. Since all of thecontacts of bank 306 except the zeroand No. l contacts are connectedtogether, the relay 255 will remain energized until the stepping switch30 has completed its cycle and its brushes have returned to their zeropositions. The reason for interrupting the circuit of transformerprimary 258 following the activation of tube 2A will be set forthhereinafter. y

At the same time that the pulse is generated in secondary 259 of thetransformer for activating discharge tube 2A a circuit is completed fromconductor 251 through conductor 263, winding of relay 264, conductor21,0, outer right-hand armature and back contact of relay 255 to ground.At its armature and back contact the relay 264 prevents the completionof a circuit which the relay 2 8 seeks to complete from ground throughits outer front contact and armature, armature and back contact of relay264, conductors 266, 2 I 2 and 3 I 2 and winding of stepping magnet 30to grounded battery. Were it not for the provision of the relay 264 thebrushes of sequence switch `30 would be stepped to their third contactat this time, which is not desired. If the relay 2 6 has a slightlyretarded operating characteristic which will not prevent it fromoperating during the time that the discharge tube 2A is conductive butwhich will permit relay 264 to operate before the relay 2 8 operates,the stepping of sequence switch 3C will be prevented.` Since theenergizing circuit of relay 264 includes the outer righthand armatureand b ack contact of relay 255, that circuit will be interrupted whenrelay 255 becomes operated and held. Relay 264 preferably has aslow-to-release characteristic such that it does not release until relay2 6 has released. Thus the relay 264 prevents the energization ofstepping magnet 30 in response to the first operation of relay 2 6, butWill not prevent such energization in response to subsequent operationsof relay 2 6 while relay 255 remains operated and held. l

The armature of relay 2BD is connected to positive battery and the backcontact with which the armature cooperates is connected to the grid sideof the input circuit of a discharge tube 2D. The input 'circuit of thetube 2D is similar to that of tube 2B, the diiference being that thesecond condenser in the circuitis in shuntl with the leakage resistoronly instead of being in shunt 4with the leakage resistance and thebiasing battery. Under the normalcondition thetube 2D is biasednegatively to cut-olf by. its biasing battery, although current isflowing through resistor 261 and condenser 268 is'charged. Upon theenergizationof relay ZBD .the positive battery is disconnected from thegrid circuit and condenser 258 discharges but tube 2Dv is not renderedcon.- ductive. Upon the release of relay 2 9 the energizing circuit ofrelay 2BD is interrupted and after an interval the relayv 2BD releases.Condenser 268 becomes recharged. and raises the potential of the grid oftube 2D so that the tube is rendered conductive. The interval duringwhich tube 2D is conductive is.y controlled by leakage resistor269 andthe second condenser 21|.

Central oice sends first selective-signal of rollA f call pleted by therelay ZY as discharge tubeZC re.

sponds to the operationl of relay 2S- As in the rst cycle of operation`of stepping switch y3B- ground is applied from-contact bank 3B3 when thebrushes step to the No. lcontact to hold relay 2W. operated and thisgroundremains connected throughout the Acycle of switch 3B. At the bank3B2 ground is applied from the brush associated with bankiG'l throughtheNo. 2 contact of that bank, No. 1 Contact and brush of bank SBZ,con-- ductor 333, right-hand armature and back. contact of relay. 3ABand winding of relay BAA to groundedbattery.. As in the` case of thelong. spacing interval after the eleventh transition as shown in Fig. 8the relays BAA and "BAB control therelays 2S and 2Z to prolong thespacing interval following the rst transition,as shown in Fig..9.Following the operation ofy relay SAB and thefrelease of relay AAthecontrol of relay 2S isrestored to relay 2Z and these relays operate invibratorymanner to transmit marking and spacingimpulses of uniformduration and to ad-` Vance the brushes. of stepping switch 3B step bystep until the brush Yassociated with bank 3132 reaches the No. l1contact which is connected to ground. This causes another cycle of therelays SAA and y3AB to control the relays 21S and ZZ to introduce a longspacing interval following the eleventh transition,y as in the firstcycle of stepping switch 3B, and this long interval is shown in Fig. 9.y

Upon the release of relay SAA rby the relay BABy relay. ZZ releasesrelay 2S to `produce a 'twelfth' transition to marking and the brushesof stepping switch 3B'are stepped to the twelfth position. The markinginterval thus produced isv only of normal length because the relay 2Sinterrupts the circuit ofrelay 2Z which releases to complete the circuitfor 2Swhich again becomes' energized to drive theploop vI2 to spacingcondition and to step the brushes.V of stepping switch 3B to the No. 13contact. In the twelfth position of the brushes of steppingI switch 3B'the brush associatedivith bank- SBS did not receive Vground connectionfrom the brush and bank'3'C3; as it did in 'the' precedingcyclebecause'the brushes of switchjCfare now on the No.` 2 contacts and thecontacts Nos'. 2`to'l1, inclusive, are connected to conta-ct l\T'o.' A14 of bank Bby' conductor 316:

' In the thirteenth positionthe brush associated with contact bank SBagain receives ground connection thistirne fromthebrush and No.2'fcontact of stepping switch bankSC" and conductor 31.4 so that;another cycle off the relays 3AA and `SAB- is iintroducedyto control therelays 2S and Zwiththe resultthat a long spacinginterval is introducedafter the'thirteenth transitionl After the, relays BAA Vand SAB 'have'operated relay 2S is released to restorethe loop |2"to marking conditionandthe brushescf sequence switch 3B are steppedto the No; ll'contacts.

'At 'contact No; llfln the bank SBS ground is applied'vfrom-"bank3C3^over conductors 316; 343 and-Mato energize relay ZXwhich in turnenergizesrelay 2V. These relays perform the same functions as previouslydescribed, namely; interruptionfoftheenergizing circuit for the relay2Sjand transfer of the energizing circuit for the stepping magnet 3B tofincludethe interrupter contacts. As thel brushassociated with'steppingswitchbank 3BE traverses contacts Nos. 15 and lgthe energizingcircuitfor the relay 2U is not completedgas it wasY in the previously describedcycle because groundgconnectionis no longer applied lto rconductor 32!onthe cont-act No. 1v of bankA BGE. Thus the brushes of stepping switchCyremainbn-their No.2 contacts while the brushes of stepping switch 3Bare rapidlyadvancedto' their zero'position.' When-the brushes reachthe'zero positionytherbrush associated with bank it` t removes theholding' ground connection from'relays, ZW and 2X which release, thelatterin turn releasing the relay 2V. Upon'the releaseof relay '2V thesamecircuit changes occur whichtookplaceupon its release at the end :of

. the preceding cyzcle ofst'epping switch'SB, namely;.preparation"of anenergizing circuit for the relay-2S,`at" the inner' left-handA armatureand back contact 'of relay' 2V, which circuit however is nowopenatthe-left-hand armature and front contact =of-relay 2W, and"preparation of an energizing circuit for the stepping magnet 3B at theright-hand,l armature and back contact of relay'EV, which circuit isopenat the armature andfront-'contactbf relay ZY and at therighthandrarmiature andv front contact lof relay 2W.

Atpits outer-left-hand armature and back contact `the relay 2V'reconnects grounded battery, still'suppliedat thebrush and No; 2contact of ycontactbanksI SC2*7 to'conductor 251. Since relay 25FahasVpreviously disconnected the primary 258 of the transformerfromconductor2 5'1 the transformer'does not'become energized; Were it notfor the provision of relay 255to interrupt the pathto transformerprimary 258, the transformergupon thel'release of relay 2V, wouldbefreoperated to render tube'ZA-conductive which in turn would 'operaterelay Z- which-in turn would operate relay EBD. Since relay ZBD renderstube 2D conductive through relay 2BC and the latter relay operatesr'elay2W to start sequence switch 3B 'through' another'cycle;v another stationcalling signal would be transmitted onloop l2 withing of stepping switch3B under the control of relay 2V.

All outlying stations react to first signal of roll call The signalcomprising the succession of impulses shown in Fig. 9 which has beentransmitted during the second cycle of the stepping switch 3B isreceivedv at all of the outlying stations associated with loop l2 andoperates the receiving line relays, such as the relay 402, in accordancetherewith. The receiving line relays operate the magnets, such as M8, ofthe step-bystep selector, and since along pause of spacing naturefollows the first impulse the contact disc of that one of the selectorswhich has a stop pin in the first step position will be held at the rststep during the long spacing interval and all of the others will berestored to normal position. It will be assumed for the purposes of thisdescription that the selector in the outlying station shown in Figs. 4and 5 is the one which holds on the rst step and all others are restoredto normal. Following the long spacing interval the transitions numbered2 to Il, inclusive, are received and step the selectors ten steps, theselectors at the station shown in Figs. 4 and 5 reaching the eleventhposition and the selectors at all other stations reaching the tenthposition. The contact discs at all of the stations except the one shownin Figs. 4 and 5 and except the one at the station which has a pin onthe tenth step will be restored to normal in the interval following theeleventh transition. The station with the pin in the tenth position willbe restored to normal following the thirteenth transition. Since, aspreviously stated, all of the selectors have a stop pin in the eleventhposition the selector shown in Fig. 4 will be held -at the eleventhposition and the relay 4S! will be operated. All of the con trols whichrelay 45| is capable of effecting were effected when the relay 4SI wasoperated in response to the signal shown in Fig, 8 and, accordingly, nofurther operations are performed except the preparation of a holdingcircuit for relays 4S2, 453 and 4S4, Following the long interval thetwelfth and thirteenth pulses are received followed by another pause ofspacing nature. The selector shown in Fig. 4 is advanced to thethirteenth position and is held by a stop pin.

First outlying station is selected At the station shown in Figs. 4 and 5a circuit is completed from grounded battery, contact disc and arm andthirteenth contact of the step-bystep selector, conductor 45|, andwinding of relay 4S2 to ground. At its left-hand armature and frontcontact the relay 4S2 completes a holding circuit through conductor 452and the lefthand front contact and armature of relay 45| to groundedbattery. The energizing circuit for the relay llSi was interrupted whenthe contact disc of the selector stepped from the eleventh to thethirteenth position but since the relay 4S! is slow to release, theholding circuit for relay 452 is in fact completed. The relay 455il alsocompletes a circuit from ground through the back contact and innerright-hand armature of relay 4S! when that relay has released, windingof relay 4B, movable front and stationary back contact of relay 4Boperable in make-before-bre-ak manner, innermost right-hand armature andfront contact of relay 4S2 which is very slow to release and thereforeholds even after relay 4S| has released, inner right-hand armatures andback contacts of relays 4S3 and 4S4, conductor 453 and winding of relay4D to grounded battery. Relays 4B and 4D both become energized but asthe relay 4B has a slow-to-operate characteristic relay `4D becomesoperated first.

At its right-hand armature and back contact the relay 4D seeks tointerrupt the holding circuit for any relay in the series 5B, thecircuit eX- tending from ground, right-hand armature and back contact ofrelay 4D, conductor 454, winding of relay 4G, conductors 456 and 556 tothe upper armatures of all of the relays in the series 5B. It haspreviously been assumed that the energizing circuit for the relay 5B!!!had been prepared but not completed. Accordingly, there had been nocircuit completed through the upper armaturesV of any of the 5B seriesrelays and the operation of the right-hand armature of relay 4D has noeffect, eitheron the relay EBI or on the relay 4G. The left-handarmature of relay 4D cornpletes the energizing circuit for the Startrelay 4ST which has a slow-to-operate characteristic. The relay 4Battracts its armature after the relay 4D has operated, establishes aholding circuit for itself from the ground at the back contact and innerarmature of relay 4st, winding of relay 4B, front contact and armatureof relay 4B, conductor 451 and outermost armature and iront contact ofrelay 4S2 to grounded battery, and interrupts the energizing circuit forthe relay 4D through the chain of armatures and contacts of relays 4S2,433 and 4S4. Ground is thus removed from the armatures at the head ofall of the chain circuits controlled by the relays 4S2, 4S3 and 4S4 sothat no other chain circuit path can be inadvertently completed.

First outlying station transmits trouble identifying signal The relay4ST upon being energized completes its own holding circuit at itsinnermost iront Contact and armature through conductors 458 and 553,front contact and armature of relay 557 to ground. At the outerright-handv armature and front contact ci relay 4ST an energizingeircuit for the transmitting relay 4T! is completed from ground at themiddle upper front Contact armature of energized relay SAIE), overconductors 524, 424, 459, outer right-hand front contact andarmature ofrelay 4ST, conductor 401, middle left-hand armature and back contact ofrelay 4C, conductor 408, inner armature and back contact of relay 4A,conductor 499, winding of relay 4TH, conductor 4H and back contact andarmature or relay 4T2 to grounded battery. The relay 4T! impresses aspacing impulse on the loop l i extending to the central oice station bymeans of its two upper armatures.

At the middle armature and front contact oi relay 4ST a circuit iscompleted from grounded battery through conductor 448, outer left-handarmature and back contact of relay 4C, conductor 441, outer armature andback contact oi relay l41A, :conductor :446, outerlower front contactofrelay lll-TI -and armature by which-it is engaged i upon the'energizationot thev relay, conductorv M4,

winding of' stepping magnet lconductor M3,

brush and zero contactiofbank ASSI; conductorl M2, front contact :andinner right-hand= armature of relay All-I to conductor 424 which isreceiving ground 'connection from the upper middle armature of relaySAID. Thus the stepping mag'- net ESS is energized preparatory tostepping its.A

rupts the energizing circuit for the relay T2 and the energizingcircuitfor stepping magnet SS at its lower armatures and front contactsso that the brushes of the sequence switch @15S are stepped to their No.l contact.

All of the contacts in the bank SSI are connected to ground with theexception of the zero contact and this is true of the bank -4SS3. Thenumbered contacts of the bank i552 are connected to the energizingwindings of the corresponding ones of the series of relays- 5B. Thus theNo. contact of bank 4SS2 is connected by conductors 623 and 523 to relayEBID as previously described. Similarly, the No. 5 contact isconnected-by conductorsliil and 555' to relay` 5B5` and the No. 1contact is connected by conductors itz and` 562 to relay EBI. Followingthe stepping of brushes -of steppingswitch SS to the No. 1 contacts,direct ground isapplied at the bank /iSSi to the steppingmagnet ASS thusproviding such ground connection independently of ythe inner right-handarmature of relay'llH and the middle upper armature of relay EAIU. Sincethe lrelay iiBl is the only relay of the 5B series, the

energizing circuit for which has beenassumed to be prepared by itsassociated '5A series relay, namely, EAIU, no electrical circuit is'completed by the brush associated with bank BSSZ over conductor 463,back contact and armature of Va relay 466, conductor iii? and energizingwinding of relay 4C to grounded battery, so that the relay @C is not atthis time energized. The brush associated with contact bank @SSSprepares, in all positions except the zero position,=a holding circuitfor the relay llC from-ground over conductor 454 to the front contactassociated with the right-hand armature of relay'llC.

Since each of the relays flTI andjllTZ interrupts the energizing circuitof the other these relays form a vibratory system which causes alternatemarking and spacing impulses to be impressed upon loop II. Each timethat relay TI is energized it completes the energizing circuit forstepping magnet BSS and each time it is released. it restores the loop II to marking condition and interrupts the circuit of magnet GSS sothatthe brushes of .stepping switch' ISS are advanced one stepimmediately following each spacing impulse. Thistransmission ofalternate impulses and advancement of the brushes continues until thebrush associated with the bank fiSSZ reaches contact No. 10 at whichtime the energizing circuit of relay 5BIO is completed over thepreviously described circuit which includes the operating winding ofrelay 4C. vAt its upper armature and front contact the relay BIcompletes its holdingcircuitthroughrelay` 4G to the ground on theright-hand armatureof relay-llD and at its lower armatureand-backcontact it interrupts theh'olding'circuit -for the relay SAID whichreleases. Relay AI releases relay v5H and removes the ground connectionfor the en- 'ergizing circuit of transmitting relay @TI so that thatrelay cannot be reenergized and the loop II extending to the centraloice station will remain .in marking condition. Although relay 5F `mayremain released to connect ground through lamp li to marking condition.The relay .4TIinter-'` 15 509, seek-ing to reenergize relay 5Al, thisrelay cannot be reenergizecl as long as the relay AEBN! remains held,which is until relay 4D becomes again energized. Relay 5G operates tointerrupt the conductive path from ground on the outer right-hand frontContact of relay fil-I to the armature neXt to the outermost of thelower armatures of relay 5H, so that with relay 5H released; theenergizing circuit for relay 5AI will not be completed. The reason forpreventing the energization of relay 5M at this time will be set at itsinner armature and back contact introduces another interruption in theenergizing cir- `cuit for the relay GTI and at its outer armature andback contact interrupts the direct energizing circuit for steppingmagnetliSS, which is also additionally interrupted at the outer lower armatureand front contact of relay GTI. At the inner left-hand armature `-andfront contact the relay 4C also completes the energizing circuitof'relay 466 inparallelwith relay 4A, and the relay 466 interrupts thecircuit through the operating winding of relay 13C; so that the circuitcannot be completedagain until relay 4C, which is now held through litsright-hand winding, is released. The purposes of relay @Sii is toprovide for the transmission of signals to identify two or more troubleconditions when they eXist at one outlying station, as will be describedlater. At its outer'left-hand'armature the relay 4C transfers thebattery connection supplied over the middle armature of relay 4ST tothestepping magnet llSS'through its interrupter contacts. The magnet 4SSthereafter operates in .buzzer manner to advance `its brushes to thezero contacts, where advancement is interrupted due to movement of thebrush SSI out of Vengagement with a 'grounded contact.

When the brush associated with bank GSSB reachesitszero Vposition itreleases the relay 4C which in turn releases the relay 4A, the relay466. The relays 3A and 4C again prepare the energizing circuit for relay[STI and the direct energizing circuit for stepping magnet SS but thesecircuits are not completed because relay remains released under thecontrol of relay BIiL From this it will be seen that ten spacingimpulses separated by marking impulses have beentransmitted to thecentral office station to Outlying station operation when two o1"- mor ltrouble conditions exist for operating the stepping magnet might bedis-` connected by relay 4ST before the advancement of the brushes hadbeen completed.

Before describing the operation of the central omce station in responseto the signal transmitted to identify the trouble condition representedby the relay SAI il the operation of the station shown in Figs. 4 and 5when two trouble conditions have occurred will be described. It will beassumed for this purpose that following the energization and locking ofrelay 5AIII under the control of relay Fbut before the completion oftransmission of the signal controlled by the relay SAID and the relay5BIIl, the relay 5D operated and attempted to complete the energizingcircuit for the relay SAS. That circuit could not be completed while therelay EAI remained energized because the` circuit was interrupted at theinnermost lower` armature and front contact of relay 5H, which was heldenergized by the relay 5AIO. Consequently, no energizing circuit for therelay SBS was prepared at the lower armature of relay SAE, so that thebrush associated with contact bank SSZ could not complete an energizingcircuit for relay 5135 as it encountered the No. 5 contact of that bank.Upon the release of relay BAIIJ as the relay 5B!!! became energizedthrough the contact bank IISSI and relay 4C, relay 5H became releasedand the effect of its release is to close the prepared energizingcircuit for the relay 5A5, which reenergizes the relay 5H and preparesan energizing circuit for the relay EBS; The relay 5A5 also appliesground through conductors 524, 324, inner right-hand armature and irontcontact of relay 4H and conductor 442 to the zero contact of bank SSI inpreparation for reenergization of stepping magnet GSS and in parallel toconductor 459, outer right-hand amature and front contact of relay 4STtothe middle left-` hand armature of relay 4C in preparation for thereenergization of relay 4TI, which at this time is prevented due to thefact that the relay 4C is energized.

Upon the arrival of the brushes of sequence switch HSS in their zeropositions, the brush associated with bank yGSSI extends the groundconnection from relay 5A5 through the stepping magnet dSS and the relays4A and 4C, upon releasing, complete the energizing circuit for thestepping magnet'and for the transmitting relay liTI. The relay 466 alsoreleases and again completes a vconductive path between the brushassociated with bank 4SS2 and the operatingwindingof relay 4C; Therelays ATI and ATZ again operate in vibratory manner to transmitalternate spacing and marking impulses to loop I I andthe brushes ofstepping switch IISS advance until the brush associated with contactbank 4SS2 reaches its No. 5 contact and completes the energizing'circuitfor relay 5B5 through relay 4C. Five spacing impulses withintervening marking impulses have beentransmitted and loop I I isthere-26 upon restored to marking condition, relay 5B5 is' locked through itsupper winding to relay 4D and the energizingcircuit of stepping magnetASS is transferred to its interrupter contacts whereby the ,brushes areadvanced in buzzer manner to their zero positions where they come torest and release relays 4A, 4C and 466.

It will now be assumed that the trouble conditions to which the relays5D and 5F are respon- 1 sive occur in the reverse order, namely, withthe and will energize the relay 5H. If they occur simultaneously, boththe relays 5A5 and EAII) will be energized and locked but only theenergizing circuit for the relay 5B5 will be prepared slncethe relay 5A5interrupts at its lower armature and back contact the conductive path tothe lower armature of relay 5AIO through which the energizing circuitfor the relay 5B| will be prepared subsequently. Relays 4TI and 4T2 areset in operation to transmit alternate marking and spacing impulses toloop II and the brushes of stepping switch IISS are advancedstep by stepuntil the No. 5 contacts are reached when relays 5B5, 4C, 4A and 466will be energized, relay 5B5 being held to the back Contact andright-hand 3U armature of relay 4D, and relay 4C being held to theground on Contact bank 4SS3 and in turn holding the relays 4A and 466.Stepping magnet SS is putin operation in buzzer manner to advance thebrushes rapidly and relay 5A5 is released by the relay 5B5, thuscompleting the conductive path through its lower armature and backcontact to the lower armature of relay 5AI`Il. If relay 5AIO had becomeenergized simultaneously with the relay EAS the release of relay 5A5results directly in preparation of the energizing circuit for relay5BIll. If the relay 5A! 0 had not become energized simultaneously withthe relay 5A5but was waiting to be energized relay 5H would be releasedby relay 5A5, relay BAI would become energized and immediatelyreenergize relay 5H and would prepare the energizing circuit for relayEBIIl. As the brushes of stepping magnet @SS in advancing rapidlyencounter the No. 10 contacts, the energizing circuit of relay EBIU isnot completed because the energizing circuit of relays 5B I l] and relay4C is interrupted at the back contact and armature of relay 466. Thusthe brushes of sequence switch ISS continue to advance in buzzer mannerto their zero positions whereupon another cycle is initiated due to thefact that relay 5A! 0 has remained energized and relay Bl has not becomeenergized and a second signal consisting of ten spacing impulses withintervening marking impulses will be transmitted while the brushes arereaching the No. 10 contact whereupon relay 5B I 0 will be operated andlocked to the relay 4D, relay EAIIJ will be released `and the brushes ofsequence switch ASS will advance to their zero positions and come torest. It will be apparent from the foregoing that the stepping switchASS will undergo one cycle of operation for each trouble condition thathas occurred prior to the calling of the outlying station shown in Figs.4 and 5 or that comes in during the transmission of trouble alarmsignals from that station and that a separate set of alternate spacingand marking impulses representing a trouble condition will betransmitted during each cycle of the sequence switch IISS. It will alsobe apparent that the signal to identify any trouble condition will notbe transmitted v.more.thanionce Withoutl specific call `1 or* .such.retransmission '-by'f the 'cen tral'- o'lce;

become locked .-totheD' relay-Which is operable 5B Il, conductor= 536;-armature f .and back` contactl 1 next to the :outermost lower: armature'of. relay.A 5H, which will be deenergizedif there-Aisne.trouA blecondition, conductoril andv/inding ofrelay' 5A| to grounded battery.-Thesrelay 5A! becomes.

operated `and held ina'mannersimilarto the relays5A5 andjEAlaoperatestherelay 5H,V and prepares an energizing circuitforv the relay-"SBR Uponthe 'operation of.- the Vrelay y 4ST. in Aresponse' to the-roll callsignal 'fori the station shown in Figs. land 5 thesystemoff'relays'dTl'.and/GT2 is started and the brushesbf stepping:sWtchSS are stepped to'the No. -`l'rcontact followingqthey rst spacingimpulseztransmitte'd to loop 'l I. the No. 1contact-ofbankf4SS2ftheenergizing circuitA for relay,` Elll. iscompleted! throughA the relay @C whereby; the 'transmission' of furtherspacing impulses: isestopped': andl` the stepping'v magnet ISS lis putintobuzvzer operationlt'o'lm-Vv store `the brushes ytothe-zerospositiorrlThe relay 5B! locks, not to then-,relay` 413i ats-inthe caseofi' therelays 5B5andf l'ebutfinstead to the -outer right-hand armaturela'nd'front-:contact v.or relay 4E.. The reason for,.this,-;is qthat ,When'the relay 5E is released under thecontrol of ajrelease. signal as willbe presently: describedgthe; relay 5B1 is i released I in ordertogpl'ace the-fs'tation. s hdwnfin Figs; 4 and 5 in suchcondition:thatfgfitis` capable of responding to -thenext roll fcallyandindicating that it istrouble-'free-if that-conditionfstill exists:

It is not desirableifto yrelease;fthefother'relays AinI the 5B. series,such as relaysY 5B15and15BI0xWhen the station release signalisfreceived'asithis would permit the ycontinuiI-igtroublesconditions:toireL assertthemselves as they did-*ein ,ther beginning.

Accordingly, the other 'relaysfinl the, 5B series; are locked to therelayyliDwsofthat;they IWillnotV be" released until after #thetroublefcondition's :have

been cleared and the station-has again-been" called7 Whether -in rollical] of all'vstaftions orby` specic individual call to test-the-stationi It should be noted thatWhen-anyonegfofrthe -relay series 5B,suchasthe lrelay SBBior 5BIO', becomes energized its :locking circuit;iscompleted through the Winding of l relay lGfWhiclithereupon :becomesoperated andhe1d',` thus interrupting the potentialenergizing circuitfcr.thefrelay' 5A l. .The purposein thusinterruptingr3thatcirr` l cuit isto'preventthetransmission/ofithe'signal indicating a trouble-freecondition-3followingthe transmission of a signal indicating avtroublecondition. When .the .holdf-relay becon-iesgenergized it completes theVenergizing circuit for the relay 5A! if there is notrouble.conditionatthe station, otherwise` it `does-not; complete tl{1ecir;-

condition lresult sin theene'rgization-of relay A5H which prevents 'theenergi'zation 'of 'relay EAI. Hovveverhfollowing the tr-ansmissionzofthe signal wheh identifies @trouble@editionthefrelyjt is released andwould thereupon complete the energizing circuit for the relayA 5A l wereitr not for `the". provision of the relay'fAG. to 'interruptsuchenergizinglcircuit. Operation of relay-{5A} following" thetransmission of'a trouble signal Woull'il,` upon'the returnotthestepping switchfbrushes to normal, restart relaysATl fand 4T2 and"the advancement of the`- 'stepping Asvviteh brushes to'effect thetransmission .ofy one spacing impulse, and the energizationand lockingof the relayV 5B1, whereby a'fal'se indication. of absenceV of a troublecondition would. be tran s`mitted.

There is the'possibility that' a troublefondition may occur after relayril-I has becomeenergized,

andib'efqefh'e .stepping swiehibrusnsee .returned to .their zeropositions incidentv to ,transl missen jof me ile-acume signal." Undefthese circumstances the v"stepping will 'Y restart immediately for ythetransmission ofthe trouble signal, 'thus f producing contradictoryreports at the` central oicefstationl The k'lfact thatutheuftrouble'condition is of 'recent occurrenceniay be deduced'from suchcontradictory reports, or the outlying station maybe recheclied, invWhich case the transmission or [the "n-trouble. signal will,

be estopped and @my the trqupiesignaiwi1ibe *transmitted Outlyingstation rez'uquistes Zine i Reference. has` previeuslrbeen made to the.fact. .thatwhen relay. 5H; becomesenersiaedit c0111.-

pletes .atil lowermost arm'atureand .front congized i through yitsinnermost front y c-orilzazlt and Wimirs' O'f" th, relai t0erguadaibatterrwhen theirelay'dsr 1sfoperated by the remy 4D. The@purpsecf the'reiayi 551l is to enablethe station show nl'in Figs. 4and'to deteririiriel when.` the transmission of all trouble sigifialsh'as'beenfcomv pletedfsgo as` to prel'zl'udeA fthe" station fromtransmittiig" signals to'identiflr troubleconditionsv Which-` niaysubsequently 'occur during Vthe roll callV ff'stations. "'.Relay4 '5l-Iisenergized las long as any relay inthe series `5A is energized and whenanyrelay in thejAV seriesjis Waiting` to be energizedfsuch Waitingbeingdue to thelfact that Ianother ofthe relays in the series is already(ilfffl gized, the relay 5H will be released on1y`long` enough for theWaiting relay to be energiaed and will be imnediatelyf'reenergized.However,

when signalsl representing all of the" trouble conditions" have beentransmitted andthe relays in thev series 5A have been released, therelay 5H willbe releasedlandwillnot be -reenergiz'ed The re1ayf`55'lWill"thereupon 'be released andafter a delay intervaliwill interrupt'the holding circuit vfor theY relay.4ST which Will release.' This Willprevent. the relay. 4T| frombeing operated under the control rof asubsequently oc-curringtrouble condition Y.sov that the `station has noWbeen deprived of vth'ejability .to transmit. troublelidentid icationsignals. -Were itfnot forthe'provision of .the release of' relayAST,following the transmission; of vsignals .appropriate to thel then`existing ,condition ofthejstat-on, the? station could at.

anyA time during z h'e roll call seize -control of .the

cuit Qf relay femmine fleafforl 12h-Bft@ liloble 755. vloonptt-extending towardfthe `cent1-a1 cnice i. and

